Grid modulated tube



1932- w. KUMMERER 1,875,025

GRID MODULATED TUBE Filed Jan. 30, 1929 n uuu u II BMWWHB nvemtoz WILHELM KUMMERER Patented Aug. 30, 1932 PATENT 0FF WILHELM KUMMERER, 0F BERLIN, GERMANY, ASSIGNOR TO TELEFUNKEN GESELL- SCHAFT FIl'B, DRAHTLOSE TELEGRAPHIE, M. B. H., OF BERLIN, GERMANY, A COR- PORATION' OF GERMANY GRID MODULATED TUBE Application filed January 30, 1929, Serial No. 336,120, and in Germany December 31, 1927.

Application for this invention filed in Germany December 31, 1927.

In the case of large-power tubes to be modulated by grid direct current, it is often found to be quite difficult to build modulator tubes which will allow the passage of the entire grid direct current in the presence of the optimum grid direct current potential and not in the presence of a positive modulator-tube grid. In other words, it is difficult to design a modulator tube having the requisite low internal resistance and still presenting sufficient slope.

It is the main object of this invention to obviate the above difliculty.

Other objects of the invention will become apparent from time to time in the following disclosure and claims when read in the light of the drawing in which:

Figure'l illustrates diagrammatically one embodiment of the invention using a separate source of current, and

Figure 2 illustrates another embodimentin which an existing source of current is utilized.

In Figure 1 of the drawing, 1 represents an electron tube having a cathode, anode and grid electrode. The output circuit of the tube comprises the circuit 2 consisting of an inductance and a capacity arranged in parallel and a source of potential 3 in series with said circuit 2. The heating current for the filament of tube 1 is provided by source 4. The input circuit of tube 1 comprises the coil 9through which the high frequency energy is impressed, and bypass condenser 10.

Connected across said condenser 10 is the I modulator tube 6. having its input circuit connected to the modulating energy source through 8. Source of potential 5 is connected in the plate circuit of tube 6 as shown.

' The filament heating current for tube 6 is supplied by'source 7.

It is seen that'the auxiliary source of potential 5 supplies an electromotive force in the path of the grid direct current of tube 1 at the plate or filament and of the modulator tube. The source 5 is connected in such a way that the supplementary electromotive force becomes added to the fall of potential occasioned by the grid direct current across the internal resistance of the modulator tube with reference to the modulator tube. In other words the potential acting at the modulator tube is increased by the value of this electromotive force.

Figure 2 shows a similar circuit as in the case of Figure 1 except that the separate source of current 5 is dispensed with and the existing source 3 is utilized by means of the potentiometer 12 as shown.

While the present invention has been shown in connection with a power amplifier tube it will be understood that the invention may also be similarly applied in circuits modulating directly in the oscillator generator circuit.

Having thus described my invention what I desire to protect by Letters Patent is as follows:

1. In a radio frequency signalling system in combination with a thermionic amplifier device having input and output electrodes and alternating current output and input circuits associated with said electrodes, asource of high frequency energy connected to said input circuit, a condenser in series with said input circuit, a source of direct current in said output circuit, a variable grid leak connected in shunt across said series condenser, said shunt connection including in series said grid leak and a portion of the direct current potential source in said output circuit.

2. In a radio frequency signalling system' in combination a space discharge device acting as an amplifier said space discharge device having input and output electrodes, and alternating current input and output circuits connected therewith, a source of high frequency energy connected to said input circuit,

a condenser in said input circuit and a source of current in said alternating current output circuit, a variable resistance device, a resistance shunted across said source of current in said output circuit and means for shunting said variable resistance and any predetermined portion of said second resistance in series therewith across said condenser.

WILHELM KUMMERER. 

